1. Field of the Invention
This application relates to a pre-stressed concrete tower for wind-power generators, particularly post-tensioned concrete, its design and constructive process, the towers include a cylinder divided in three substantially equal semi-circular sectors, arranged to form a pyramid. The three concrete sectors are joined together with concrete prefabricated slabs forming a triangle, to form a tower having variable cross-sections, which ends in a circular section at its upper end. Both the semi-circular segments and the slabs are pre-fabricated into sections that allow them to be erected, joined together and attached to a foundation, by prestressing cables. The prefabricated parts, because of their size, can be fabricated on-site, thus avoiding the need to be transported.
2. Description of the Related Art
Towers of several designs have been proposed for wind-power generation. For example, several different towers have been built, having metal structures based on armatures; also, they have been built with tubular sections. In both cases, their height is limited because of their dimensions, the turbulence caused by the air, their strength against intense earthquakes, and their ease of building, because in many cases it is not practical for the heights presently used.
Also, towers of the prior art are known such as those described in U.S. Pat. No. 2,826,800, on a conical tower built into concrete segments joined by tension elements.
Also, the German utility model DE 29809540U describes a segmented pre-stressed concrete tower for wind-energy generators. According to this publication, conical frustrum (i.e., truncated conical) segments are fabricated in-plant, which later are erected and joined together. According to the publication, towers of two hundred meters' height, or more, can be erected in this way.
According to International Patent WO-2004/007955, a construction system for conical segmented towers is described. This publication describes the use of molds for in-shop fabrication of each concrete segment. The concrete segment includes a series of ducts. When the segments are erected, pre-stressing elements are run into the ducts to protect their structural integrity.
The segmented-concrete tower systems of the prior art, each have at least the following drawbacks. Frustro-conical segments require one mold for each segment that is to be constructed. Moreover, because of their sizes such molds are complex and costly, some of them having approximately 6.5 meters in diameter and 4 meters' in height. In addition, they must be used in a facility for pre-fabricating the concrete segments. The transportation to the site of these pre-fabricated sections, which can weigh more than 60 metric tons, must be carefully planned, using thereby big cranes and flatcars adequate for their size. Because there are a multiplicity of different molds, the joining of the pieces is a difficult factor, requiring complex devices to accomplish this joining. This is the case of Patent WO-02/04766. The erection of these sections must be done with large-capacity cranes, using very high scaffolds, which influences the cost of said erection.